10. Foot care

CHAPTER 10. Foot care

Christine Skinner

Introduction 217

Foot health education 218

Assessing the diabetic foot 218

Treatment and management of foot lesions 226

Infection 228

Ulceration 230

Conclusion 241

References 242

INTRODUCTION

The foot is a complex structure that is not only responsible for locomotion but is also designed to withstand the stresses of body weight while walking and standing. These stresses can result in microtrauma, which can lead to foot lesions. Foot problems are still the most common cause of hospital admissions for people with diabetes in the UK (Young et al 1994) and the length of stay is greater than for any other diabetic complication (Williams 1985). Foot disease remains one of the most common and devastating of diabetic complications, being responsible for a considerable amount of healthcare resource in the UK (Scottish Intercollegiate Guidelines Network (SIGN) 55 2001). The estimated cost for ulceration and amputation in the UK in 2001 was £244 million (Shearer et al 2003). Diabetic foot disease often arises as a result of neuropathy, ischaemia, structural deformity or a combination of two or all of these factors.

Overall 20–40% of people with diabetes have neuropathy and 20–40% have peripheral vascular disease (Hutchinson et al 2000). Neuropathy and peripheral vascular disease develop as a result of poor blood glucose control and adverse risk factors such as smoking and dyslipidaemia (Hutchinson et al 2000). People with diabetes must also be aware of the influence of good glycaemic control, as hyperglycaemia can affect the microvascular status (UK Prospective Diabetes Study (UKPDS) 1998).

Any minor trauma occurring in the foot can easily become infected and, if not managed correctly, can lead to the development of cellulitis, osteomyelitis and ultimately amputation. Of those people with diabetes, 5–7 % will develop a foot ulcer at some time in their life (SIGN 2001).

As complications associated with the diabetic foot have been described as a ‘major medical, social and economical problem’ of global proportions (Boulton & Vileikyte 2000) , it is imperative that all those involved in the care of the people with diabetes are familiar with aspects of care in the diabetic foot.

Foot complications can be associated with social deprivation, poor vision, disability, foot deformity and absence of professional foot care (Hutchinson et al 2000). All of these factors can influence the person’s ability to practise good foot care; however, there are two key aspects of foot care:

1. assessing the foot

2. treating foot lesions.

The management of the person should always have a multidisciplinary approach with close liaison between podiatrist, diabetologist, general practitioner, diabetes nurse specialist, the primary and community care nurse and orthotist.

Treatment by a podiatrist is free to all those with diabetes within the UK. The podiatrist should be involved in the care of the person with diabetes soon after diagnosis and thereafter as the individual is referred to them. It is recommended that people with diabetes only attend those podiatrists in the UK who are registered with the Health Professions Council.

FOOT HEALTH EDUCATION

Foot health education plays an important part in any successful management strategy. People who have had diabetes for many years may be unaware of the potential problems that can affect their feet. It must be remembered that whereas individuals with diabetes should be aware of these problems, it is important that they are not caused unnecessary alarm. It is essential, therefore, to gain the individual’s confidence and trust and to establish a rapport. In so doing, the practitioner will be able to gauge the levels of knowledge and understanding the person might have. Reassurance is essential to minimise the individual’s anxiety and re-enforcement of foot health education optimises self management.

ASSESSING THE DIABETIC FOOT

The multidisciplinary team must be aware of the guidelines published by National Collaborating Centre for Primary Care (National Institute for Health and Clinical Excellence (NICE) 2004) and of the Scottish Intercollegiate Guideline 55 (SIGN 2001) in caring for the feet of a person with diabetes.

Primary care nurses might be involved in assessing the foot for diabetic complications as part of the annual screening visit or as part of their everyday care for these individuals. GPs might also be involved in assessing the feet at the screening clinic. It is important to record the outcome of findings to allow subsequent monitoring of the person’s feet.

Before examining the feet, certain facts should be ascertained:

▪ duration of diabetes

▪ does the person have type 1 or type 2 diabetes?

▪ present level of glycaemic control

▪ do they experience pain or cramping in their legs when walking?

▪ do they have a numbness or tingling sensation in their feet?

▪ Is there a history of foot ulceration?

▪ does the person smoke?

▪ Is there any visual handicap?

Foot assessment requires some skills and experience in examining and interpretation. Examination of the foot involves assessment of soft tissues, structural deformities, vascular and neurological status and it is essential to assess and compare both lower limbs and feet.

SOFT TISSUE ASSESSMENT

This involves assessing both the skin and the nails.

Skin

When assessing the colour of the skin a comparison of the feet should be made. The colour and temperature of the skin are indicative of the blood flow through the foot. The skin of a foot with a good blood flow will be pale pink and warm to touch. If there is impaired blood flow the skin will be cold and pale. Cyanosis indicates a poor oxygen content and therefore poor blood supply. The appearance of a cold, hyperaemic (bright red) foot demonstrates ischaemia to the peripheral tissues and should be considered as a potential problem. The skin of an ischaemic foot is shiny, stretched, hairless and cool to touch.

The foot should be examined for the presence of soft tissue lesions such as callus, corns and any abrasions or indications of trauma. The interdigital spaces are often macerated and are a potential site for fungal infection and should not be overlooked.

People with autonomic neuropathy in their feet will have decreased sweating which results in dry, devitalised skin. The plantar aspect of the foot and the heel area are often affected, with the posterior aspect of the heel liable to fissuring providing a potential site for infection to develop.

Nails

The nails can vary in appearance depending on the vascular state of the foot. In the ischaemic foot the nails may be thickened and slow growing. If they are infected by fungi they will appear thickened, discoloured and have a ‘musty’ smell (Figure 10.1). The nail grooves should also be examined to ensure that no callus or small spike of nail has penetrated the soft tissues of the groove, which can lead to an infected in-growing toenail (Figure 10.2). Nails that have been cut inappropriately can cause damage to the adjacent toe.

Fig. 10.1The diabetic foot: nails thickened and discoloured by fungal infection

Fig. 10.2Infected in-growing toenail

STRUCTURAL DEFORMITIES

Structural deformities as a complication of diabetes act as a potential site for ulceration because the area is subjected to abnormal stresses. The combination of sensory neuropathy and increased pressure on the plantar aspect of the metatarsal heads may result in ulceration (Pham et al 2000).

The toes are often in a clawed position as a result of motor neuropathy, which causes wasting of the small intrinsic muscles and allows the long flexors to have an unopposed action (Figure 10.3). The metatarsal heads therefore become much more prominent on the plantar surface and are subjected to greater stress during walking leading to the formation of hyperkeratosis. The dorsal aspect and tips of the toes are also liable to develop corns.

Fig. 10.3Clawing of the toes as a result of motor neuropathy: long flexor muscles have unopposed action because small intrinsic muscles are wasted

Structural deformities might also be present in the diabetic foot as a result of changes from Charcot neuropathic joints (Armstrong et al 1997). In the Charcot foot, pain perception and the ability to sense the position of the joints in the foot are severely impaired or lost, and muscles lose their ability to support the joint(s) properly. Loss of these motor and sensory nerve functions allow minor traumas such as sprains and stress fractures to go undetected and untreated leading to ligament laxity, joint dislocation, bone erosion, cartilage damage, and deformity of the foot. The bones most often affected are the metatarsals and the mid-foot (Figure 10.4).

Fig. 10.4Charcot foot

VASCULAR ASSESSMENT

The diabetic foot can be affected by both macrovascular and microvascular disease. Both have significant influences on the clinical appearance and the subsequent management of the foot. Symptoms of vascular insufficiency should be elicited from the individual. If the person complains of intermittent claudication, its severity can be assessed by determining how far the individual can walk before symptoms develop. It is also necessary to determine if the person suffers from pain when at rest, which is an indication of severe ischaemia.

It is essential to distinguish the pain of ischaemia from that of neuropathy, which often presents as a burning sensation.

Clinical assessment of the vascular state can be carried out routinely by performing a variety of physical tests. All members of the healthcare team, after suitable training, should be able perform these tests. To meet national guidelines, assessment must be carried out annually. People who are identified as ‘at risk’ following a vascular assessment should be referred for a more detailed peripheral arterial assessment (Stuart et al 2004, Watkins 2003).

PHYSICAL TESTS

Palpation of pulses

Peripheral circulation can be assessed by palpation of pedal pulses (Figure 10.5):

▪ The dorsalis pedis artery is a continuation of the anterior tibial artery. The pulse can be palpated on the dorsal aspect of the foot in the region of the intermediate cuneiform.

▪ The anterior tibial pulse can be palpated on the front of the ankle mid-way between the two malleoli.

▪ The posterior tibial pulse can be palpated immediately behind the medial malleolus.

Fig. 10.5Palpation of pedal pulses

Confidence is essential in palpating pedal pulses, and such confidence is only acquired through practice. All members of the healthcare team need to be encouraged to develop this skill with normal, healthy people before progressing to people with known vascular complications. A hand-held Doppler can also be used.

It should be noted that arteriovenous shunts will develop due to autonomic neuropathy and, as a result, blood flow bypasses the capillary bed. Thus people might have bounding arterial pulses but have poor blood supply to the surrounding tissues. This is responsible for the venous engorgement often seen on the dorsum of the foot (Ward & Boulton 1987).

Temperature gradient

The temperature gradient can be assessed by gently running the back of the hand from below the knee distally to the toes. If there are any obvious changes intra- and interlimb, these should be noted.

Capillary refill

This is assessed by gently pressing the plantar aspect of the hallux until it blanches. Pressure is removed and the tissues allowed to reperfuse. Normal capillary refill should be 3 seconds.

Presence or absence of oedema

The presence of oedema can prevent the palpation of pedal pulses. If present, the affected sites should be noted.

Presence or absence of varicose veins

Varicose veins can lead to oedema of the ankle or dorsum of the foot and create a problem with socks and shoes. Any varicose veins should also be noted.

NEUROLOGICAL ASSESSMENT

Neuropathy is a major contributory factor in the development of ulceration in the diabetic foot (Thomson et al 1991). Neuropathy can affect sensory, motor or autonomic function. The most common diffuse neuropathy affecting people with diabetes is distal symmetric sensorimotor polyneuropathy (Boulton 2000). Some people with diabetes present with painful neuropathic symptoms; alternatively, this can develop over the following years. The person suffering from neuropathy can present with varying symptoms. He or she might complain of pain, which can be burning, sharp shooting or lancinating; paraesthesia; numbness with loss of pain; hot or cold sensations or irritation from bedclothes. Other unusual sensations might also be experienced and individuals might complain of the ‘feeling of cotton wool under their toes’ or ‘walking on hot sand’. If the person complains of pain it is important to distinguish the pain from that of ischaemia by assessing the quality of the pain and by examining the peripheral circulation.

If there is neuropathy present then a thorough structural assessment must be performed. This determines areas of pressure that might result in the development of callus and corns and eventually ulcers (Pham et al 2000).

Neuropathy might also result in damage to the soft tissue of the foot because, having lost sensation, the individual is unaware of trauma to the foot. Hence people are advised not to walk around on bare feet (Box 10.1 and Box 10.2). Prior to the neurological assessment being undertaken it is essential what is involved is explained to the person with diabetes. It is also useful to let the person experience the perceived sensation on an area where there is no sensory loss.

Box 10.1

Foot health education for the person with healthy feet

▪ Never walk barefoot

▪ Change hosiery daily

▪ Wash feet daily, dry carefully in between the toes

▪ Apply a cream to the soles and heels

▪ Inspect feet daily for corns/callosities/plantar warts/athlete’s foot

▪ If any of the above is present, they should only be treated by a registered podiatrist

▪ With the slightest abrasion or infection in your feet, contact your GP, community nurse, diabetic nurse specialist, diabetic consultant or podiatrist

▪ Never use proprietary treatments for callus or corns, as they contain acids

▪ Cut toenails straight across

▪ Buy new shoes from a shop that measures your feet and fits the shoes for you

▪ Never wear new shoes for a long period of time

▪ Stop smoking

▪ Only attend a podiatrist registered by the Health Professions Council

Box 10.2

Foot health education for the person with an ‘at risk’ foot

▪ All of Box 10.1 plus:

▪ Do not cut your own toenails

▪ Inspect feet daily for any open lesions, cracking, dryness, change in colour, swelling, corn, callus, blisters, warts or signs of infection

▪ Use a mirror to inspect the soles of your feet or ask someone to look for you

▪ Only use a hot water bottle to heat your bed: never place it next to your feet

▪ Never sit close to the fire or heater

▪ Check inside shoes for foreign objects

▪ Wear shoes with soft uppers, preferably lacing

▪ Never wear garters to hold up stockings or socks

Light touch

This can be assessed using a piece of cotton wool. The person’s foot is gently touched with the cotton wool and sites identified where it can/cannot be appreciated. This commences distally and moves proximally, thereby moving from a potentially numb area to a normal area. It is easier to identify the boundary of sensory loss when moving from a numb area to an area of normal sensation. The person should have his or her eyes closed during this examination. Ensure that there is minimal variation in the pressure of application of the cotton wool. Note that the cotton wool should not be run across the tissues as people with paraesthesia can experience discomfort and pain.

Sharp and blunt sensation

A Neurotip can be used to identify if sharp and blunt sensation is present or absent. Again, the person’s eyes should be closed during this examination and the assessor should commence distally and work proximally.

Pressure

Pressure can effectively be assessed using a 10-g Semmes–Weinstein monofilament in predicting the risk of foot ulceration (Abbott et al 1998). Monofilaments are cheap and easy to use, making them an ideal screening tool. The sites tested are usually defined by local protocols but are generally agreed to be plantar aspects of the hallux, first, third and fifth metatarsal heads, heel and apices of the fourth and/or fifth digits; these are the most common sites for ulceration to develop. The monofilament is calibrated to buckle when a force of 10 g is exerted and if the person cannot feel the pressure the foot is considered to be insensate. The greater the number of negative responses identified, the greater the risk (Baker et al 2005).

It is important to ensure that any areas of hyperkeratosis are removed before carrying out this test (Figure 10.6).

Fig. 10.6Monofilament

Vibration

Vibration perception can be assessed using a standard 128-Hz tuning fork or a Reydell Sieffer tuning fork with a graduated scale, which will give a recordable measurement. Sites that should be assessed are the ankle, first metatarso-phalangeal joint and the plantar of the hallux. The person should have his or her eyes closed for this assessment. He or she should experience a buzzing sensation and indicate when this can no longer be felt. A neurothesiometer can also be used and will give a quantifiable reading but this is an expensive piece of equipment not available to many practitioners.

Autonomic neuropathy

Individuals with autonomic neuropathy usually have dry and flaky skin on their feet, and sometimes fissuring in the heel area. This can be a potential site for bacterial infection, which might result in ulceration.

Other tests, which require specialised equipment, can be used to enhance the examination of the diabetic foot. These are usually carried out by the podiatrist. The purpose of assessing the diabetic foot under the various parameters outlined above is to determine the foot which is ‘at risk’ and undertake a management strategy according to SIGN (2001).

The ‘at risk’ foot may, therefore, be defined as the foot which has any one of the clinical signs detailed inbox 10.3

Box 10.3

The ‘at risk’ foot has any one of these clinical signs

▪ Ischaemia

▪ Numbness

▪ Structural deformities

▪ Callus and/or corn

▪ Absence of pedal pulses

▪ A capillary refill time in excess of 3 seconds

▪ Limb pain and/or paraesthesia

▪ Intermittent claudication

▪ History of foot ulcers

▪ Loss of sensation of light touch, sharp and blunt touch

Further detailed instructions in foot health care (see Box 10.2) should be given if the person is assessed as having an ‘at risk’ foot. Patient education in the prevention of foot problems is the first line of defence. The individual’s ability to understand the importance of foot health education should be assessed. The person should also receive regular podiatry care and be made aware of a system for seeking immediate medical attention if a foot problem arises. All healthcare professionals must continually reinforce appropriate foot health education.

TREATMENT AND MANAGEMENT OF FOOT LESIONS

People can present with a wide range of foot problems. Some people require only routine nail cutting and simple advice on foot care (see Box 10.1). Others will have nail problems, callus, corns or even ulceration and will require more intensive care and education (see Box 10.2).